1. Field of the Invention
The present invention relates to a colorant material containing two or more types of organic colorant compounds, and a water dispersion and an ink containing the colorant material, an ink tank, a recording unit, a recording apparatus and a recording method using such a water dispersion and ink. The water dispersion can be used as a recording material.
2. Related Background Art
As life style has been changed with the progress of science and technology, colorants (also called “color materials”) have been not only used as conventional coloring agents for materials such as fibers, plastics and leather but also used in various industrial fields by taking an advantage of the feature of the colorant suitable for data recording or data display. With rapid spread of personal computers in recent years, hard copy technique represented by ink-jet printing has been developed in order to record (print) letters and image data output from the computers.
The ink-jet printing technique has been developed, with the result that it exceeds silver halide photograph in terms of image quality; however, the stability of images with time is not yet sufficient. As color materials for use in ink-jet ink, dyes or pigments are used. In the former case, a highly accurate image in quality can be provided; however, storage stability is poor. In the latter case, a relatively good image can be obtained in view of weather resistance; however, a color reproduction range is narrow and thus its image quality is usually poorer than that obtained by dye-based ink. Color fading of these color materials is conceivably caused by light, moisture, and activated gases in the environment such as ozone. In these circumstances, it has been desired to develop a novel color material excellent in fastness having a high weather resistance.
As means for improving light fastness of an image obtained by ink-jet ink, various methods have been proposed in which additives such as an ultraviolet absorbent, light stabilizer and antioxidant are used in order to give functionality to the ink (see Japanese Patent Application Laid-Open Nos. H11-170686, 2002-317135 and 2002-348512). Unfortunately, although weather resistance (light fastness) is improved by any method, its effect is not always sufficient. This is considered that since additives are not present in the proximity of colorants, the ink is not sufficiently functionalized by the additives and the effect of the additives are not produced well.
An attempt to improve the light fastness of an image obtained by ink has been made by use of a water-soluble liquid composition that is composed of an oil-soluble additive and a water-soluble dye (see Japanese Patent Application Laid-Open Nos. 2000-327941 and 2001-64554). However, this method has a problem in that the compatibility between the oil soluble additive and the water-soluble dye is not sufficient, and therefore usually has a limited effect.